Method of determining where pipe is stuck in a well



arch 24,1942. c. H. JO'HNSON METHOD OF DETERMINING WHERE PIPE IS STUCK IN A WELL 2 Sheets-Sheet 1 Filed Dec. 31, 1938 March 24, 1942. c JOHNSON 2,277,110

METHOD OF DETERMINING WHERE PIPE IS STUCK IN A WELL Filed Dec. 31, 1938 2 Sheets5heet 2 INVENTOR Patented Mar. 24, 1942 Curtis E. Johnson, Santa Monica, Calif.

" Application Deccmber'31, 1938, Serial No. 248,818

8 Claims.

This invention relates in general to the art of drilling bore holes in the earth, and in particular it relates to methods of determining the point or points in a bore hole at which pipe is stuck.

Heretofore there have been two general methods of determining where pipe is stuck in a well. One method consists in lowering a fishing string and jar-down spear, taking hold inside the pipe at intervals, jarring, and noting the change in character of the "vibrations produced in the pipe. Under ideal conditions, when the spear takes hold above the stuck point, the jarring produces a metallic ringing sound that is absent when the jarring occurs below the stuck point.

The other method consists in applying tension to the top of thepipe by means of the hoisting block, hook, and elevator, or other hoisting means available, and measuring the stretch of the pipe as a function of the applied tension. From this function, the weight per lineal foot of the pipe, Youngs modulus for the material of the pipe, and Hookes law, an attempt is made to compute the depth to the stuck point.

In the first method described above, difficulty is frequently encountered in getting the jardown spear to take hold inside the pipe. Further, on rotary rigs means for jarring is frequently absent or improvised. An added disadvantage is that in many cases the pipe is more or less frictionally restrained along its entire length, and the metallic ringing sound is damped out at depths much shallower than the actual stuck point.

In the second method described above, difficulty is caused by slipping of the pipe at the stuck point when tension is applied. A further difliculty occurs in the interpretation of the results of the stretch test, since it is practically impossible to evaluate properly the effect of the distributed friction between the pipe and the walls of the bore hole.

. It is an object of this invention to provide a.

' suitable apparatus for carrying out themethod Itisa of the invention. Another object of this invention is toteach how to interpret the record obtained as a result of the method of this invention.

Other aims and objects of the invention will appear from the following description in which:

Figure l is a section of a bore hole showing the relation of the apparatus of this invention to such portions of the customary drilling equipment as seems necessary for an understanding of the invention.

Figure 2 shows an operable form of the recording apparatus of this invention.

Figure 3 is a detailed view of a means of attaching the pickup means to the outside of the pipe.

Figure 4 is a sectional view of a pair of impact members applied to the outside of the pipe as are the pick-ups of Figure 3.

Figure 5 is a view of means for attaching the pick-up means to the inside of the pipe, showing the clamped position.

Figure 6 shows the unclamped position of the device of Figure 5.

Figure 7 is a view of means for attaching impact means to the inside of the pipe, showing the clamped position.

Figure 8 shows schematically a typical record obtained by the method of this invention.

The following detailed description of the method includes certain apparatus to facilitate the understanding of the method, though it is to be understood that the method is not limited to the use of the described apparatus.

In Figure 1, formation I is penetrated by'a bore hole with walls I which is cased for part of its depth as by easing l0 cemented tothe walls of the bore hole as by cement seal ll. Within the bore hole and the casing, drill stem 2 is suspended as by swivel 6, bail I, hook 8, spring 9, and other hoistingmechanism, not shown, above and supportingspring 9. For illustrating the present invention, drill stem '2 is shown as being partially frictionally restrained by the walls of the bore hole at l3 and I4, and completely. restrained, or stuck, at l5 as by shale stratum l5 slumping into the bore hole around the drill stem. At some point below stuck point l5, bit 4 is attached to the lower end of drill stem 2.

It will be observed 'that drill 'stem 2 is composed of a plurality of lengths of pipe joined together as by collar joints or tool joints 3. It is convenient, though not necessary, as will later appear, that drill stem 2 be unrestrained by rotary table l2 as shown. U

- In the method of this invention, not only is stuck point l5 located, but partially restrained points such as l 3 and M are also located. This is accomplished by striking the drill stem a sharp reflection from Joints 3, stuck point I5, partially restrained points I3 and I4, and, under some conditions, from bit 4. Various means for imparting the impulse to the drill stem and for receiving the reflections may be employed. In

Figure l operable means for performing these functions are shown attached to the outside of the drill stem at I6 and I! respectively.

Means i1 is shown in greater detail in Figure 3. It comprises a triple clamp, portion 23 clamped around drill stem 2, and portions 21 and 21' clamped around vibration pick-ups l8 and I8".

respectively. Vibration pick-ups l8 and I8" are preferably of one of the types most sensitive to vertical components of vibration. The vertical seismometer is an example of such a vertically responsive pick-up; I prefer to employ two such pick-upsconnected in series as shown by output conductors 28, 23 and 30 in order that the combination of the two may be insensitive to transverse components of vibration of the drillstem, though this feature is not essential to the operation of the method of the invention.

Means I6, shown in section in greater detail in Figure 4 than it is in Figure 1, comprises a central clamp, such as clamp 26 of Figure 3, and a pair of solid members 2'|a and 2|'-a in place of clamps 21 and 21' of Figure 3. Each member has a striking surface, such as 3|; for striking as with a hammer, and a hollow recess, such as 32', open at the top, in which to detonate a small amount of explosive such as an electric blasting cap. To avoid creating transverse comtwo electric blasting caps 50' and 50" are shown connected in parallel to leads 53' which function to detonate caps 50' and 50" as leads 53 of Figure 7 function to detonate cap 50 as hereinafter described.

Instead of mounting the impulse imparting and receiving means on the outside of the drill stem, it may be advisable to mount them inside the drill stem, as by the means shown in Figures 5, 6 and 7. Referring to Figure 5, pick-up I8 is provided withrigidly attached bevelled wing portions 33 slidably connected to bevelled gripping portions 34 as by flared tongues 33 and grooves 35. Gripping portions 34 are .provided with lugs 40 to which are attached cables 4| which join to form cable 4|. Pick-up I0 is provided with a lug 43 to which" is attached cable 44. when pick-up l8 and associated portions 33 and 34 are lowered into the drill stem, their weight is supported by cable 44, whereupon gripping portions 34 slide downward and inward to the limit of their motion relative to pick-up I3 and wing portions 33, as shown in Figure 6. By

proper choice of dimensions, the inward motion of gripping portions 34 may be made sufficient to permit the entire assembly to drop past any normal decrease in the internal diameter of the drill stem-such as an internally upset joint.

When the pick-up and gripping assembly has descended to the desired point in the drill stem,

ance against losing the entire pick-up assembly due to unforeseen slippage of the gripping portions, it is well to provide the upper end of cable 4| with a hook 42 which may be hooked over the edge of the drill stem, though cable 4| should be left slack in order that all vibrations reaching the pick-up will do so via the walls of drill stem 2 in contact with gripping portions 34.

A similar assembly for imparting an impulse at a point on the inside of the drill stem is shown in Figure 7. This assembly is similar to that shown in Figures 5 and 6 except that it is provided with a solid wedge-shaped portion in place ofpick-up l8 and its attached bevelled wing portions 33. Portion 46 is provided at its center with a threaded taper pin 41 to which may be screwed a drilling jar (such as the type used in cable tool drilling) for imparting impulses to the drill stem. If a sharper or larger impulse is desired than can be obtained with the jar, a block' 48, containing on its upper face a recess 32, may be screwed onto pin 41, and a small amount of explosive, such as an electric blasting cap 50, placed in the recess and detonated as by an electric current originating in battery 5| and flowing through battery 5|, key 52, leads 53 and cap 60 upon the completion of the circuit by closing key 52.

Figure 2 illustrates schematically how the impulses received by the pick-up are recorded. The details cf the elements are well known in the arts of sound recording and reflection seismograph geophysics and, since they form no new part of the present invention, they are not here shown. No power supply is shown for the elements, it being assumed that they contain their own batteries.

From the pick-up l8, or the combined pickups l8 and IS", the electrical transduction of the'vibration is conducted to time-gain-control l9, from there to amplifier 20, and from there to recorder 2| where the properly amplified impulses are recorded on record strip 23. Ordinarily, photographic recording is preferred, which yields latent image 24 of the impulses received. Optionally a timer signal may be generated by timer 22, conducted to recorder 2|,

and recorded as latent image 25 on record strip 23 concurrently with latent image 24.

Due to internal molecular and external surface friction the impulse which travels in the drill stem gradually decreases in amplitude as a function of time. In the method of my invention I prefer to vary the electrical amplification as an increasing function of time of such nature as to substantially offset the above decrease. This is accomplished by time-gain-control l3 whose construction and operation are well known in the art of reflection seismograph geophysics. To avoid special means for coordinating the beginning of the time-gain-control cycle and the initiation of the impulse, I prefer to trip an electrical relay in any conventional manner with the first impulsereceived, said relay opening the battery circuit which starts the time-gain-control cyc e.

Since the velocity of propagation of elastic waves in the drill stem is on the order of 16,000 feet per second, the speed of the recording strip may conveniently be on the order of 20 inches per second, which is sufficiently close to the recording speeds employed in-sound recording and in refiection seismograph geophysics to permit the adaptation of recorders from these parallel arts to the method of this invention. If a time scale is employed it may conveniently take the form of a record of the vibrations of a thousand cycle fork.

Figure 8 schematically shows a typical record obtained by the method of this invention. Both the timer record 25' and the reflection record 24' are shown on record strip 23, though under many circumstances the timer record is superfluous as will hereinafter be shown. Referring to reflection record 2%, the first passage of the impulse past the pick-up is recorded as impulse t9. Only the fact that the time.-gain-control is in its most insensitive condition prevents impulse $9 from being excessively large. Even so, it is usually much larger than any subsequently recorded reflected impulse.

Reflected impulses are recorded as at 3-41, 3-1), 3-0, I3--a, 'l l--a, l-a, and l-a. As indicated by their regular spacing and relatively uniform wave shape, 3-a, 3-4), and 3-c, are reflections from pipe joints. In the example shown reflections 3a are from joints 3 in drill stem 2 above the first partially restrained point l3. Reflections 3-b are from joints in drill stem 2 between partially. restrained points l3 and I4. Reflections 3-c are from joints in drill stem 2 between partially restrained point M: and stuck point 55. In the region 3d, reflections from joints in drill stem 2 below stuck point l5 are of such small magnitude as to ordinarily be imperceptible, though a reflection 4-a from bit t on the bottom end of the drill stem may be visible under certain circumstances.

Reflections l3-a, Hla and I5-a. are from points of restraint as indicated by their spacing and wave shape not being in accord with that of reflections 3-41, 3-4), and 3--c. In the example shown reflection l3-a is from partially restrained point 13, reflection lt-a is from partially restrained point I l, and reflection i5-a is from stuck point 115.

The magnitudes of waves I3-a, M-a and l5--a as shown are entirely arbitrary. Under certain circumstances they may be either larger or smaller than the reflections from the joints of the drill stem. Also, they may vary considerably from the shape of the reflections from neighboring joints of the drill stem.

From a study of the amplitude and wave shape of the reflection from a restrained point, and from a comparison of the amplitudes of the reflections from joints immediately above and below it, much can be deduced about the nature of the restraint. If there is a marked decrease in the amplitudes of the joint reflections below a restrained point as compared with those above, the restraint is a major one. If the reflection from the restrained point is sharp, the restraintis a suddenly applied or discreet one. If the reflection from the restrained point is elongated in time, or is absent, the restraint is more gradually applied along the drill stem. Little can be deduced from the amplitude of the reflection from a restrained point without also taking the wave shape into consideration. However, of two reflections from restrained points having the same wave shape, the one which is largest compared to the drill stern joint reflections immediately above it indicates the greatest restraint. I

The above directions for interpreting the record obtained by the method of this invention are merely illustrative of some of the inferences which may be drawn from the record by those skilled in the art of interpreting such records, and must not be construed as placing any limitation on the method of my invention.

Though the description of the method and the particular apparatus for carrying out the method have dealt with measurements on a drill stem, the same general technique may be applied to measurements on casing or any other pipe for determining its condition in relation to the walls of the bore hole, or the arrangement and location of its joints or the technique may be applied with modifications evident to those skilled in the art to measurements on any buried or hidden pipevor rod-like body of substantially higher velocity of propagation and lower rate of vibratory energy dissipation for elastic waves than the medium surrounding it.

Though a timer record 25' is illustrated in conjunction with the reflection record 24' in order that the total travel distance of the received impulses may be calculated by multiplying their travel times by the velocity of propagation of elastic waves in the pipe, this procedure will frequently be unnecessary, for in many wells the number and distance apart of the pipe joints is known, and thus the pattern of pipe joint reflections provides all the distance scale that is needed.

I have described the method of my invention in terms of certain operable apparatus, but other operable apparatus is now, or may be in the future, known to those skilled in this or parallel arts. Thus it will be understood that many changes may be made in the means for carrying out the method of my invention, and even in the details of the method itself, without departing from the spirit of my invention as defined in the following claims.

I claim:

l. In a method of determining the condition of a pipe in a bore hole, the improvement which comprises imparting to the solid material forming the wall of the pipe at a point adjacent the upper end thereof an impulse which travels downward in the pipe wall and is partially reflected upward at reflection points at different depths in the pipe wall, at least one of the reflection points being at an unknown depth, receiving the reflected impulses at a point adjacent the upper end of the pipe, and measuring the time required for impulses to travel from the point of impulse origin to the respective reflection points and-from there to the receiving point.

2. In a method of locating the depth at which a pipe is bound in a bore hole, wherein the bound point affects the transmission of a vibratory impulse in the pipe wall along the length thereof and past the bound portion, the improvement which comprises imparting to the wall of the pipe at a point adjacent the upper end thereof a vibratory impulse which travels downward in the pipe wall and is partially reflected upward in the wall from reflection points of known character located in the pipe wall at known depths above and below the bound point, receiving the reflected impulses at a point above the bound point, and determining which reflection points are above and which reflection points are below the bound point by relating the character of the received impulses to the character of the reflection points.

3. In a method of locating a point at which a pipe is stuck in a bore hole, the improvement which comprises the steps of initiating an impulse in the wall of the pipe near its upper end, thereby causing the impulse to travel downward in the pipe wall to reflection points in the wall,

at least one of the reflection points being at a stuck point at an unknown depth, receiving near said upper end the impulses reflected from the reflection points, and measuring the time required for the impulses to travel in the wall from the upper end to the reflection points, including at least one reflection point at the unknown impulses at a point above the bound portion of the pipe and measuring the time of travel'ofthe impulse in the wall from the point of the wall at which the impulse is initiated to the bound portionand from there to the receiving point.

5. In a method of determining the condition of a pipe in a bore hole, the improvement which comprises imparting to the wall of the pipe a vibration impulse that travels in the pipe wall to a reflection point at an unknown position therein and is there at least partially reflected, receiving the reflected impulse, and measuring the time of travel of the impulse in the pipe wall.

6. In a method of determining, the condition of a portion of a pipe in a bore hole, the improvement which comprises imparting to the wall of the pipe a vibration impulse that travels in the pipe wall to reflection points encountered before and after traversing the pipe portion and is there at least partially reflected, receiving the reflected straint, the improvement which comprises imparting to the wall of the pipe at a point adjacent its upper end a vibratory impulse which travels downward in the pipe wall and is partially reflected upward in thewall from the respective pipe joints, receiving at a point above the restrained portion impulses which are reflectedfrom joints above and below a restrained portion of the pipe, amplifying the received impulses, varying the factor of amplification as such a function of the time elapsed since the initiation of the impulse to the times of reflected impulse reception so as tosubstantially offset the normal decrease in amplitude of the received waves in the pipe in the absence of any restraint thereon, recording the reflected waves, and determining the nature of the restraint by comparing the amplitudes of the reflected waves received from joints above and below the restrained point.

8. In a method of determining the condition of a pipe in a bore hole, the improvement which comprises imparting to the wall of the pipe a.

longitudinal vibration impulse that travels in the pipe wall to a reflection point at an unknown position therein and is there at least partially reflected, receiving the longitudinal component of the reflected impulse, and measuring the time of travel of the impulse in the pipe wall.

.' CURTIS H. JOHNSON. 

